KR20150003800A - Composite materials - Google Patents

Abstract

A layer of reinforcing fibers impregnated with a curable resin matrix, and a plurality of electrically conductive composite particles located adjacent to or proximate to the reinforcing fibers. Each of the electrically conductive composite particles is comprised of a conductive component and a polymeric component wherein the polymeric component is initially solid and substantially insoluble in the curable resin but experiences at least partial phase transition to the fluid phase during the curing period of the composite ≪ / RTI >

Description

COMPOSITE MATERIALS [0002]

In the aerospace industry, the use of composites is becoming more and more important as a large number of primary and secondary structures in aircraft frames are made of composites. The advantages of composites in aircraft design include high strength-to-weight ratios, excellent fatigue durability, corrosion resistance and flexibility, and allow for significant reduction of components and the need for fasteners and joints. However, the application of these materials to the primary and secondary structures of modern aircraft presents a particular challenge due to the dielectric nature of the resin matrix. Although the use of carbon fibers as reinforcing fibers in composites can convey some electrical conductivity along their length due to their graphitic properties, the dielectric properties of the matrix resin in the composite material can be attributed to the overall electrical conductivity of the composite and the structure . Composites with increased electrical conductivity are required for aircraft primary structures to meet stringent requirements for lightning protection, potential discharge, electrical grounding, and electromagnetic shielding.

The electrical conductivities of the resins and composites can be improved by incorporating other conductive particles or polymers within the resin matrix or interlayer regions of the composite structures. Such a state of the material solutions in the field may be used to improve the z-direction conductivity of the composite rather than its mechanical performance. By "z-direction" is meant the direction in which the reinforcing fibers are perpendicular to the axis through the thickness of the planar or composite structure arranged in the composite structure.

The present invention is directed to fiber-reinforced composite materials that can provide improved peel and impact resistance properties as well as high conductivity in the thickness direction. According to one embodiment of the invention, the fiber reinforced composite material comprises:

i) at least one structural layer of reinforcing fibers impregnated with a curable resin matrix; And

Ii) at least one electrically conductive composite particle adjacent or in close proximity to said reinforcing fibers.

The electrically conductive composite particles are micron sized particles comprised of at least one electrically conductive material dispersed in a polymeric material. As described above, the conductive composite particles each have a conductive component and a polymeric component. The polymeric component of the electrically conductive multiparticulates is initially solid and substantially insoluble in the curable resin matrix prior to curing of the resin matrix but it may undergo at least partial phase transition into the fluid phase during the curing period of the resin matrix. The curable resin matrix of the structural layer may be a curable composition wherein the polymeric component in the conductive composite particles is at least partially soluble during the curing period of the resin matrix.

A method of making a multilayer composite structure having conductive composite particles in interlayer regions is also disclosed.

Another aspect of the present invention relates to conductive polymeric fibers and nonwoven structures having properties similar to conductive composite particles.

Figure 1 schematically illustrates an electrically conductive composite particle according to one embodiment of the present invention.
Figure 2 illustrates an exemplary method of producing electrically conductive composite particles.
Figure 3A schematically illustrates a composite structure containing electrically conductive particles within interlayer regions prior to curing.
Figure 3b schematically illustrates the composite structure shown in Figure 2a after curing.
4 is a scanning electron microscope (SEM) image showing micro-sized conductive composite particles prepared according to one embodiment of the present invention.
Figures 5a and 5b are two micrographs showing cross-sectional views of a cured composite structure based on incorporation of copper / polyamide composite particles within the interlayer region.
Figure 6 is a micrograph showing a cross-section of a cured composite structure based on incorporation of conductive copper / PES particles in the interlayer region.

"Third generation reinforced composites" has recently been developed for primary structures in the aerospace sector. The impact resistance of such materials is improved by alternating polymer interleaf between fiber-reinforced strands. The presence of interlayer polymeric particles, fibers or films can significantly reduce the electrical conductivity in the " z-direction " of the fiber-reinforced composite material due to the dielectric properties of the materials. Therefore, in order to ensure an acceptable level of potential discharge and electrical grounding to avoid potential catastrophic failures of composite components or accidents associated with fuel vapor ignition in lightning events and subsequent fuel tank explosion, the term "third generation materials" It is necessary to improve the composite z-direction electrical conductivity.

The electrical conductivity of the resin-based composite can be improved by incorporating different conductive particles or polymers into the resin matrix or into the interlayer regions of the multilayer composite materials and structures. Metallic fillers can be used at high loads (typically greater than 50 wt%) to reduce resin resistance, but this approach generally results in significant weight gain and substantial reduction in mechanical properties. Conjugated conductive polymers can improve resin system conductivity at relatively low loads, but they endanger the thermo-mechanical performance of structural resin systems and prepregs for the aerospace sector. Carbon-based additives such as carbon black, carbon nano-tubes, carbon nano-fibers may be used to modify the composition of resin systems, but they present processing-ability and dispersion difficulties, To limit their use.

Recently, a series of interlayer particles with a conductive coating has been proposed as a solution to create an electrical bridge between two adjacent layers. However, such conductive particles can usually only provide high electrical conductivity or impact resistance characteristics, but can not provide both.

The present invention provides a multifunctional solution comprising a curable resin matrix having reinforcing ability and one or more structural layers of reinforcing fibers impregnated with electrically conductive composite particles. Moreover, when such conductive composite particles are used in interlayer areas of multi-layer composite structures, they can create electrical bridges between the structural fiber layers within the multi-layer composite structures. The solution of the present invention provides an improvement in mechanical properties such as fracture toughness and impact resistance, as well as an improvement in the z-direction conductivity of the composite structures. The term " conductive composite particles " will be used hereinafter to refer to " electrically conductive composite particles ". The conductive composite particles are micron-sized particles comprised of at least one electrically conductive material dispersed in at least one polymeric material. As such, the electrically conductive composite particles each have an electrically conductive component and a polymeric component.

When a plurality of composite materials are laminated and cured in a multi-layered configuration (i.e., lay-up), the polymeric component of the conductive composite particles dissolves in the resin matrix of the structural layers, thereby releasing the conductive component, Creating a controlled interlayer region and a conductive bridge between the layers. Such a material solution can simultaneously improve the impact resistance and peel strength of the multi-layer composite structure, while allowing currents such as those generated by lightning to diffuse or diverge across a wide range of composite structures, It is possible to reduce the possibility of fatal damage to parts. Moreover, the conductive composite particles can potentially be an effective solution to mitigate or eliminate lightning direct effects, particularly edge glow phenomena in third generation composite structures. Finally, electrically conductive composite particles can provide additional advantages in terms of composite electromagnetic performance. Composite particles based on highly conductive and / or magnetic fillers can be used as a flexible tool for adjusting the electromagnetic interference (EMI) shielding efficiency, dielectric constant and transmittance properties of composite structures.

Conductive composite particles

1 schematically shows a conductive composite particle according to one embodiment of the present invention. Although FIG. 1 shows spherical particles, it should be understood that the electrically conductive composite particles of the present invention can be any suitable shape, including but not limited to spheres, spheroids, ellipses, cubes, polyhedrons, Dimensional structures. Moreover, the particles may have a well-defined geometry, or the shape may be irregular.

The average particle size (d 50) of the conductive composite particles is less than 150 μm, preferably in the range of 10-90 μm, more preferably in the range of 10-60 μm. d50 represents a median value of the particle size distribution, or alternatively, 50% of the particles have a particle size at or below this value.

The conductive component of the conductive composite particles may include metallic materials having an electrical conductivity of more than 1 x 10 ³ S / m, non-metallic conductive materials, and combinations thereof. Suitable metallic materials include any known metals including, but not limited to, silver, gold, platinum, palladium, nickel, copper, lead, tin, aluminum, titanium, alloys and mixtures thereof. Preferably, the metallic materials have electrical conductivities in excess of 1 x 10 ⁷ S / m, more preferably in excess of 3 x 10 ⁷ S / m. Suitable non-metallic conductive materials include, but are not limited to, carbon or graphite-based materials.

When the conductive material is metallic, the conductive component is present in an amount ranging from 1% by weight to 90% by weight, preferably from 30% by weight to 85% by weight, and more preferably from 50% By weight to 80% by weight. When the conductive material is non-metallic or carbon-based, the conductive component may be present in the range of 1 wt% to 75 wt%, preferably 1 wt% to 25 wt%, based on the total weight of the conductive composite particles .

The polymeric components of the conductive multiparticulates are initially solid at room temperature (i.e., 20 ° C to 25 ° C) or insufficient for substantially complete curing of the resin matrix and are insoluble in the curable resin matrix (ie, host resin matrix) But may also include one or more polymers capable of undergoing at least partial phase transition to the fluid phase during the curing period of the host resin matrix. During the curing cycle, the polymeric component dissolves into the resin matrix upon contact with the resin matrix. In other words, the polymeric component has no (or negligible) solubility in the curable resin matrix at room temperature or under conditions insufficient for full curing of the resin matrix (e.g., during prepreg preparation) (I. E., Dissolved more than 50%) or overall (i. E., Fully dissolved) during the curing cycle of the resin matrix.

The term " cure " or " cure ", as used herein, refers to the formation of a resin by crosslinking of the polymer chains resulting from chemical additives, ultraviolet radiation, microwave radiation, electron beam, gamma radiation, or other suitable thermal or non- It means strengthening the matrix.

As discussed in this context, the solubility characteristics of the polymers for polymeric components in the host curable resin matrix can be determined by a variety of known methods, including optical microscopy, spectroscopy, and the like.

For one material to be dissolved in another material, the difference in their solubility parameters (delta) must be as small as possible. The solubility parameter for the polymer can be determined by calculation based on the group contribution method (see Van Krevelen DW Van Krevelen, Properties of Polymers, 3rd Revised Edition, Elsevier Scientific Publishing, Amsterdam, 1990, Chapter 7, pages 189-224) .

The solubility parameter of the polymer may be determined using Hansen Solubility Parameters (HSP) as a method of predicting whether a material will dissolve in another material to form a solution. The Hansen parameters are based on the concept that a molecule is "defined as" such that "it dissolves as" is another one when it is bonded to itself in a similar manner.

Polymers suitable as polymeric components of the conductive composite particles may be selected from homopolymers or copolymers with functionalized or non-functionalized thermoplastic resins alone or in combination with thermosetting resins. Suitable thermoplastic materials can include any of the following: polyurethane, polyketone, polyamide, polyphthalamide, polystyrene, polybutadiene, polyacrylate, acrylic, polymethacrylate, polyethersulphone, (PES), polyetheretherketone (PES), polyetheretherketone (PES), polyetheretherketone (PES), polyetheretheresulphone (PEES) sulfone sulfone, polyester, liquid crystal polymers, polyimide, polyetherimides , PEEK), polyaryl ethers, polyaryl sulfides, polyphenylene, polyphenylene oxide (PPO), polyethylene oxide (PEO), polypropylene oxide alone or combinations thereof Also included are elastomers (including segmented elastomers) or thermoplastic polymers A combination of elastomeric polymers.

Preferably, the polymeric component is selected from functionalized thermoplastic polymers that are miscible with suitable thermosetting matrices, have a high modulus and a glass transition temperature (Tg), and are rigid. In general, thermoplastic polymers having a Tg of at least 150 캜, preferably more than 200 캜, are suitable.

The number average molecular weight of the thermoplastic polymers may range from 2000 to 60,000. Preferably, it is greater than 9000, such as 11,000 to 25,000. The presence of these thermoplastic polymers in the host thermosetting resin increases the toughness of the cured thermosetting resin by providing strong thermoplastic zones between the cross-linked thermosetting zones. The functionalized thermoplastic polymer preferably contains pendant or chain-terminating functional groups which will chemically react with functional groups in the thermosetting resin composition to form covalent bonds, ionic bonds or hydrogen bonds. Such functional groups can be obtained by reaction of the monomers or by subsequent conversion of the product polymer prior to or subsequent to isolation. Preferably, the functional groups of the thermoplastic polymer have the formula:

-A-Y

Here, A is a divalent (divalent) a hydrocarbon group, preferably aromatic, Y is 'a or SH, where R' groups, especially OH, NH _2, NHR to provide an active hydrogen-containing carbon atoms of eight or less Or a hydrocarbon group which provides other crosslinking reactivity, especially monomers containing epoxy, (meth) acrylate, cyanate, isocyanate, acetylene, ethylene vinyl, allyl, benzoxazine, anhydride, oxazoline, maleimide and saturate.

The polymeric component of the conductive multiparticulates may be applied to undergo a complete or partial phase transition, for example, may be completely dissolved, or may be partially dissolved. &Quot; Partially dissolved " means that a portion of the polymer component dissolves into the matrix while another portion retains its basic or original shape. To ensure that the time and temperature of procuring are insufficient for complete dissolution or as a blend or copolymer with one or more insoluble polymers in the form of a random or block copolymer, As derivatives of the compounds or as blends therewith.

In another embodiment, the polymeric component may comprise a mixture of a thermoplastic resin and one or more thermosetting resins, and optionally one or more curatives and / or catalysts for thermosetting resins. Suitable thermosetting materials include epoxy resins, addition-polymerized resins, especially bismaleimide resins, acrylic, unsaturated polyester, vinyl ester resins, cyanate ester resins, isocyanate modified epoxy resins, But are not limited to, benzyl photopolymers, formaldehyde condensate resins (e.g., with urea, melamine or phenol), polyesters, acrylics, reaction products and combinations thereof.

Method for producing conductive composite particles

The conductive composite particles of the present invention can be produced by a single- or multi-step process. In one embodiment, the particles are produced by a two-step process, which comprises an initial high-shear blending step followed by a particle-size reduction step of dispersing the conductive component into the polymeric material. One exemplary method for producing the conductive composite particles is illustrated in FIG. The conductive material 31 and the polymeric material 32 are compounded in an extruder 33 to form pellets. It should be understood that " conductive material " may include one or more conductive materials, and " polymeric material " may include one or more polymers. In such an embodiment, the polymeric material and the conductive material may be fed into the extruder simultaneously or sequentially, preferably to form a homogeneous physical blend of the conductive material and the polymer. The starting polymeric material 32 being introduced into the extruder may be in the amorphous phase or in the form of a melt.

The starting conductive material for the preparation is selected from known metals including but not limited to silver, gold, platinum, palladium, nickel, copper, lead, tin, aluminum, titanium, alloys and mixtures thereof . Moreover, the starting conductive material can be any suitable shape and form such as flakes, powders, fibers, spheres, dendrites, disks or any other three-dimensional shape, either alone or in combination, of a micrometer or nanometer dimension have. Preferably, the starting conductive material has a high specific surface area and a low apparent density. The conductive component preferably has a density of 2.0 g / cm < ³ > , And the specific surface area (SSA) is preferably more than 0.1 m ² / g. Examples of suitable metallic material is low density 525 nickel flake ^{(AD = 0.65 g / cm 3} USA) , available from Novamet Specialty Products Corp, CAP 9 is (silver) powder ^{(SSA = 3.0 m 2 / g} , Johnson Matthey, UK (AD = 0.6-0.7 g / cm < ³ >, SSA = 0.23 m < ² >, available from Johnson Matthey, UK) and CH- ² / g, available from GGP Metalpowder AG, Germany).

The starting conductive material for producing the particles may be carbon or graphite-based materials, such as carbonized, short carbon fibers, graphite flakes, graphite nano-platelets, carbon black, single- Walled carbon nanotubes (DWCNT), multi-walled carbon nanotubes (multi-walled carbon nanotubes), single-walled carbon nanotubes -walled carbon nano-tubes, MWCNT), carbon nano-fibers, carbon nano-spheres, carbon nanorods, fullerenes, carbon nano-ropes, carbon nano- Nano-needles, carbon nano-sheets, graphens, carbon nano-cones, carbon nano-scrolls with scroll-shaped features, boron nitride-based products. These " nano- " structures refer to structures having a diameter or minimum dimension of less than one micron.

The starting conductive material may be selected from the coated products. The coated product includes a core-shell structure having an organic or inorganic core and one or more conductive shells that may or may not be conductive. Suitable metal-coated products include metal-coated graphite flakes, metal coated polymers, metal coated fibers, metal coated ceramics, metal-coated glass, metal-coated hollow glass spheres, carbon- , Carbon-coated polymers, carbon-coated fibers, carbon-coated ceramics.

Examples of non-metallic conductive materials include NC7000 multi-wall carbon nano-tubes (available from Nanocyl, Belgium), Micrometer 3775 graphite flakes (SSA = 23.7 m ² / g, Asbury Graphite Mills, Inc., USA), Micrometer 4012 synthetic graphite flake (SSA = 1.5 m ² / g, available from Asbury Graphite Mills, Inc., USA). Examples of coated products is Novamet Specialty Products Corp., USA (AD = 1.7 g / cm 3 - 1.9 g / cm 3) - is coated graphite flakes obtained from a nickel.

The temperature in the extruder should be adjusted for the optimum rheology of the composition in the extruder for the type and amount of conductive material added. In a preferred embodiment, the temperature profile is in the range of about 90 캜 to about 350 캜. A variable temperature profile can be used along the length of the extruder. Optionally, additives, diluents, dispersants, pigments or stabilizers can be added to the polymer / conductive blend to improve the stability, processability and dispersion of the conductive material in the polymeric material.

The extruder may be equipped with conventional low or high shear / mixing profiles or combinations thereof depending on the type and content of the filler and the polymer rheology behavior. In one embodiment, a sequence of conventional mixing screw sections of low shear may be used to achieve a satisfactory level of dispersion. In a preferred embodiment, the extruder is equipped with a high-shear screw profile with conventional mixing segments associated with chaotic mixing units to create an optimal balance between shear and pressing forces within the barrel to optimize dispersion levels, The process conditions can be achieved by using a prismatic TS24HC extruder equipped with a 24 mm co-rotating twin screw system with an LD ratio of 40 to 1. Two different feed systems with different feed screws to accommodate different materials (conductive material or polymer pellets) may be used. A screw speed and specific temperature profile of approximately 200-300 RPM in multiple heating zones can be used to achieve a maximum torque of 60% to 95% for a given blend. Other methods may be used to disperse the conductive material into the polymeric material using conventional techniques known to those skilled in the art, such as mechanical mixing, ultrasonic treatment, high-shear mixing, rotor stator mixing and sol- Can be used.

The production process of the composite particles may include a particle size reduction / micronization step. The undifferentiation can be accomplished using conventional techniques known in the art, such as rotary impact milling, Rotoflex milling (i.e., milled in a Rotoplex grinder manufactured by Hosokawa Micron Co., Ltd.), rotary classifier milling, ball milling , Fine milling in contra-rotating pin mills (e.g. Alpine Contraplex available from Hosokawa Micron Ltd), fluidized bed in contrast to jet milling, spiral-flow jet milling, cryogenic milling. In a preferred embodiment, the pellets from the extruder 33 (FIG. 2) are then used to produce powders of micro-sized particles having an average particle size of less than 150 [mu] m or, in some embodiments, less than 60 [ Is dispersed in an Alpine cryogenic milling system (34) equipped with rotary grinding media.

Cryogenic milling is a size reduction process in which the polymer is produced in a cryogenic liquid (usually liquid nitrogen, liquid argon) or brittle at a cryogenic temperature and milled sequentially. The cryogenic grinding process has proven to be a cost-effective and energy-efficient method of reducing the risk of thermal damage caused by volatilization or overheating of components while producing powders with a fine and controlled particle size distribution. A specific sequence of steps using studs, beaters, swing beaters and plate beater disks is generally being developed to achieve micronized particles representing the desired average particle size distribution (d50).

Composites and structures

The conductive composite particles of the present invention can be used as interlayer particles between fiber-reinforced polymer layers, e.g., prepreg piles. Thus, in this context, the host resin system is a resin matrix of fiber-reinforced polymeric layers or prepreg files.

The host resin matrix may be a curable / thermosetting composition wherein the polymeric component of the conductive composite particle is at least partially soluble during the curing period, wherein phase transfer to the fluid phase is caused by dissolution of the polymeric component in the resin matrix . Initially, when the conductive composite particles are in contact with or dispersed in the host resin matrix during mixing or during the prepreg manufacturing process, the composite particles are in a solid phase and are insoluble in the host resin matrix. During the curing cycle of the composite / resin matrix, the polymeric components of each composite particle are substantially or completely dissolved in the host resin matrix, thereby releasing the conductive component as unique free-flowing structures within the composite interlayer region. It should be understood that, in some cases, the polymer component can not be completely dissolved (but is substantially dissolved) after curing, and accordingly, the conductive component may adhere to the small residue of polymeric material that is not dissolved. In some embodiments, phase-separation between the polymeric component and the host resin matrix occurs during the cure cycle of the host resin matrix.

The host resin matrix (or resin system) in which the polymeric components of the composite particles are soluble during curing is selected from epoxy resins, bismaleimide, vinyl ester resins, cyanate ester resins, isocyanate modified epoxy resins, phenolic resins, One or more uncured thermosetting resins, including, but not limited to, phenols, phenols, benzaldehyde, formaldehyde condensate resins (e.g., with urea, melamine or phenol), polyesters, acrylics, ≪ / RTI > In one embodiment, the host resin matrix is a thermoset composition wherein at least 50% of the polymeric component of the conductive multiparticulates is soluble during curing of the resin matrix. Suitable epoxy resins include aromatic diamines, aromatic mono-primary amines, aminophenols, polyhydric phenols, polyhydric alcohols, polyglycidyl derivatives of polycarboxylic acids. Examples of suitable epoxy resins are polyglycidyl ethers of bisphenols, such as bisphenol A, bisphenol F, bisphenol S and bisphenol K; And polyglycidyl ethers of cresol and phenolic novolacs.

Specific examples include tetraglycidyl derivatives of 4,4'-diaminodiphenylmethane (TGDDM), resorcinol diglycidyl ether, triglycidyl-p-aminophenol , Triglycidyl-m-aminophenol, bromobisphenol F diglycidyl ethers, tetraglycidyl derivatives of diaminodiphenylmethane, trihydroxyphenylmethane triglycidyl ether, phenol-formaldehyde novolak Polyglycidyl ether of o-cresol novolac, or tetraglycidyl ether of tetraphenyl ethane.

Commercially available epoxy resins suitable for use in the host resin matrix include N, N, N ', N'-tetraglycidyldiaminodiphenylmethane (eg, MY 9663, MY 720, and MY 721 from Huntsman) ; N, N, N ', N'-tetraglycidyl-bis (4-aminophenyl) -1,4-diisopropylbenzene (eg Momentive to EPON 1071); N, N, N ', N'-tetraglycidyl-bis (4-amino-3,5-dimethylphenyl) -1,4-diisopropylbenzene, (eg from Momentive to EPON 1072); triglycidyl ethers of p-aminophenol (e.g., MY 0510 from Hunstman); triglycidyl ethers of m-aminophenol (e.g., MY 0610 from Hunstman); Diglycidyl ethers of bisphenol A-based materials such as 2,2-bis (4,4'-dihydroxyphenyl) propane (e.g. having a viscosity of preferably 8-20 Pa · s at 25 ° C DER 661, or Momentive to EPON 828, and Novolak resins); Glycidyl ethers of phenolic novolak resins (e.g. DEN 431 or DEN 438 from Dow); Di-cyclopentadiene-based phenolic novolacs (e.g., Tactix 556 from Huntsman); Diglycidyl 1,2-phthalate (e.g., GLY CEL A-100); Diglycidyl derivatives of dihydroxy diphenylmethane (bisphenol F) (e.g., Huntsman to PY306). Other epoxy resins include cyclic aliphatic, such as 3 ', 4'-epoxycyclohexyl-3,4-epoxycyclohexanecarboxylate (e.g., Huntsman to CY 179).

Generally, the host resin matrix comprises one or more thermosetting resins in combination with other additives such as curing agents, curing catalysts, co-monomers, rheology modifiers, tackifiers, inorganic or organic fillers, elastomers In order to modify the properties of the resin matrix before and after curing, it is also possible to modify the properties of the reinforcing core-shell particles, stabilizers, inhibitors, pigments, dyes, flame retardants, reactive diluents, soluble or particulate thermoplastics, In combination with other additives well known to the skilled artisan.

The addition of the curing agent (s) and / or catalyst (s) in the host resin matrix is optional, but the use of such materials can increase the cure rate and / or reduce the cure temperature if desired. The curing agent is suitably selected from known curing agents, for example, aromatic or aliphatic amines, or guanidine derivatives. Aromatic amine curatives are preferred, aromatic amines having at least two amino groups per molecule are preferred, and diaminodiphenylsulfones are particularly preferred, for example when the amino groups are in the meta- or para-position relative to the sulfone group . Specific examples include 3,3'- and 4-, 4'-diaminodiphenylsulphone (DDS); Methylenedianiline; Bis (4-amino-3,5-dimethylphenyl) -1,4-diisopropylbenzene; Bis (4-aminophenyl) -1,4-diisopropylbenzene; 4,4'methylenebis- (2,6-diethyl) -aniline (MDEA from Lonza); 4,4'methylenebis- (3-chloro, 2,6-diethyl) -aniline (MCDEA from Lonza); 4,4'methylenebis- (2,6-diisopropyl) -aniline (from Lonza to M-DIPA); 3,5-diethyltoluene-2,4 / 2,6-diamine (D-ETDA 80 from Lonza); 4,4'methylenebis- (2-isopropyl-6-methyl) -aniline (M-MIPA from Lonza); 4-chlorophenyl-N, N-dimethyl-urea (e.g., Monuron); 3,4-dichlorophenyl-N, N-dimethyl-urea (e.g. Diuron 占 and dicyanodiamides such as Amicure 占 CG 1200 from Pacific Anchor Chemical).

Bisphenol chain extenders such as bisphenol-S or thiodiphenol may also be used as curing agents for epoxy resins. Examples are 3,3'- and 4-, 4'-DDS.

Also suitable curing agents are anhydrides, especially polycarboxylic anhydrides such as nadic anhydride, methylnadic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, Hydroxycarboxylic anhydride, hydrophthalic anhydride, and trimellitic anhydride.

Figures 3a and 3b illustrate one embodiment in which conductive composite particles are incorporated into a composite structure. 3A, a plurality of conductive composite particles 20 are dispersed in the interlayer regions 21, 22 formed between the curable, composite layers 23, 24, 25. Each of the composite particles 20 contains a mixture of a metallic material and a polymeric material. Each of the composite layers 23, 24, 25 is comprised of reinforcing fibers impregnated with a curable resin matrix (i.e., uncured or not fully cured). The resulting laminated material is then applied to curing. Upon curing of the stack of composite layers, the polymeric component 20 of the conductive composite particles undergoes a partial or complete phase transition into the fluid phase and is completely or substantially impervious to the resin matrix of the composite layers 23, 24, 25 Thereby releasing the metallic material into the interlayer region as shown in Figure 3B. When the composite layers 23, 24, 25 contain conductive reinforcing fibers, for example carbon fibers, the released metallic material forms electrically conductive bridges between the layers of z-direction reinforcing fibers.

&Quot; Interlamineral zone " means an area between adjacent layers of reinforcing fibers in a multi-layer composite structure. Each fiber layer is impregnated with one or more polymeric materials. Such a layer may be referred to as a " fiber-reinforced polymer layer ". The fiber-reinforced polymeric layer may take the form of a prepreg. The term " prepreg " as used herein includes a sheet or layer of fibers impregnated with a resin matrix within at least a portion of their volume. The prepregs used to make aerospace structures are generally resin-impregnated sheets of reinforcing fibers aligned in one direction and are often referred to as " tapes " or " unidirectional tapes. &Quot; The resin matrix may be present in a partially cured or uncured state. The prepregs may be fully impregnated prepregs or partially impregnated prepregs. Typically, the prepreg is in a form ready to be molded and cured into a final composite portion and is typically used to produce load-bearing structural components such as wings, fuselage, bulkheads and control surfaces of aircraft. Important properties of the cured prepreg are high strength and stiffness due to reduced weight.

A plurality of prepreg files may be laid up in stacking order to form " prepreg-up ". The prepreg files in the layup may be positioned in a selected orientation relative to each other, e.g., 0, 45, 90, and so on. The prepreg layups may be fabricated on techniques that include, but are not limited to, hand layup, automated tape layup (ATL), advanced fiber placement (AFP), and filament winding. . ≪ / RTI >

Suitably, the curing of the composite structure or prepreg layup generally suppresses deformation effects of escaping gases or inhibits void formation at elevated temperatures up to 200 DEG C, preferably in the range of 170 DEG C to 190 DEG C Preferably from 3 bar (0.3 MPa) to 7 bar (0.7 MPa), by the use of elevated pressure, preferably up to 10 bar (1 MPa). Preferably, the curing temperature is obtained by heating to 5 占 폚 / min, for example, from 2 占 폚 / min to 3 占 폚 / min, and up to 9 hours, preferably up to 6 hours, And is maintained for a required period of time from 2 hours to 4 hours. The use of catalysts in the resin matrix may allow much lower curing temperatures. Pressure is released everywhere, and the temperature is reduced by cooling to 5 [deg.] C / min, e.g., up to 3 [deg.] C / min. Post-curing can be carried out at a temperature in the range of 190 DEG C to 350 DEG C and at atmospheric pressure, and a heating rate suitable for improving the glass transition temperature of the resin matrix is used.

To produce high-performance composite materials and prepregs, suitable reinforcing fibers can be characterized in general terms with a tensile strength in excess of 100,000 psi and a modulus in excess of two million psi. Fibers useful for this purpose include fibers formed of carbon or graphite fibers, glass fibers and silicon carbide, alumina, titania, boron, etc., as well as organic polymers such as polyolefins, poly (benzothiazole) Such as polyacrylates, polyacrylates, poly (benzoxazole), aromatic polyamides, polyaryl ethers, and the like, and may include mixtures having two or more such fibers. Preferably, the fibers are selected from glass fibers, carbon fibers and aromatic polyamide fibers, such as those available under the trade name KEVLAR by DuPont Company. The fibers can be used as continuous unidirectional or multi-directional tapes, or as fabrics, non-crimped, non-woven fabrics, in the form of cracked, selectively discontinuous and continuous tows of a plurality of filaments. The fabric type can be selected from plain, satin or twill styles. Non-crimped and multi-axis shapes can have many files and fiber orientations.

The conductive composite particles are present in an amount ranging from 0.1% by volume to 25% by volume, and preferably from 5% to 15%, based on the total resin content of the composite structure. In certain embodiments, the conductive composite particles can be used in combination with non-conductive interlayer strengthening particles. In such embodiments, the combination of conductive particles and non-conductive particles may be present in an amount of up to 25% by volume based on the total resin content of the composite. The non-conductive interlayer strengthening particles may comprise functionalized, non-functionalized or crosslinked elastomeric or thermoplastic particles. Suitable materials for non-conductive particles include, but are not limited to, polyimide materials (e.g. P84), emulsified poly (phenylene oxide) materials (e.g. EPPO 16), poly (phenylene oxide) materials (PPO), carboxy- Nitrile (CTBN), polyamide (nylon), poly (etheretherketone) (PEEK). The non-conductive thermoplastic particles can be selected from the group consisting of crosslinked thermoplastic particles, such as crosslinked polyethersulfone (PES), crosslinked polyetherether sulfone (PEES), crosslinked polyetherimide (PEI), crosslinked polyphenylene oxide (PPO), or crosslinked copolymers thereof.

Composite materials and methods of making the structures

The composite materials of the present invention can be produced using different processes.

Generally, a method of incorporating conductive composite particles into the production of composite materials comprises:

(a) dispersing at least one conductive material in a polymeric material to form a composite blend;

(b) optionally heat treating the blend;

(c) forming micron-sized conductive composite particles from the composite blend;

(d) optionally heat treating the micron-sized conductive composite particles;

(e) forming a stack of composite materials incorporating conductive composite particles in at least one interlayer region between adjacent layers of reinforcing fibers, wherein each composite material comprises at least one fiber-reinforced polymeric layer Wherein the fiber-reinforced polymer layer is comprised of reinforcing fibers impregnated with a curable resin matrix.

In one embodiment, the conductive composite particles are deposited onto the surface of the prepreg ply prior to laminating multiple prepreg files together to form a stacked stack ready for curing. The composite particles can be deposited by any conventional techniques, such as sparging, electrostatic deposition, scatter coating, spray distribution, and any other technique known by those skilled in the art. The dispensed composite particles adhere to the surface of the prepreg due to the viscosity of the resin. When the prepreg files are laminated together to form a laminate panel, the particles remain in the interlayer areas of the laminate panel.

In another embodiment, a certain amount of conductive composite particles are mixed with a curable / uncured resin matrix prior to prepreg preparation. In such an embodiment, the resin films are first prepared by coating the particle-containing resin mixture onto a release paper. The resulting resin film is then laminated onto a layer of fibers with the aid of heat and pressure to impregnate the fibers, thereby forming a prepreg ply having a specific fiber area weight and resin content. During the lamination process, the conductive composite particles are filtered out and remain outside of the fiber layer due to the fact that the size of the particles is greater than the spacing between the fibers. The two layers of prepregs containing conductive composite particles are then placed in the interlayer region between two adjacent prepreg files when one layer is deposited on top of the other. The polymeric components of the conductive multiparticulates are negligible under normal prepregging conditions or have no solubility.

In an alternative embodiment, the curable resin composition without conductive composite particles is coated onto release paper to form a resin film, which is in turn brought into contact with one or two different surfaces of the fibrous layer. The resin impregnates the fibers and leaves little or no resin on the outer surface of the fiber layer. Subsequently, the second film of the curable resin containing conductive composite particles is brought into contact with the outer surface of the resin-impregnated fiber layer. Additional films of the curable resin containing conductive multiparticulates may be brought into contact with the different outer surfaces of the resin-impregnated fiber layer to form a sandwich structure. As a result, the conductive particle-rich resin layer is left outside of the impregnated fiber layer and does not further impregnate the fibers. A plurality of such structures are stacked together to form a composite structure with the conductive composite particles within the interlayer regions.

In another embodiment, the two films of the curable resin composition without conductive composite particles are in contact with different surfaces of the fiber layer. The resin impregnates the fibers and leaves little or no resin on the outer surface of the fiber layer. Subsequently, the second film of the curable resin containing conductive composite particles is brought into contact with the opposing surface of the pre-impregnated fiber layer. A plurality of such structures are stacked together to form a composite structure with the conductive composite particles within the interlayer regions. Such an approach is desirable because it tends to provide a well-aligned laminate that results from particles that do not interfere with the arrangement of the fibers.

The composites, structures or prepresses formed by these methods may be in the form of continuous lengths or lengths of tapes, toes, or webs.

Alternative Example

According to another aspect of the present invention, the conductive blend and the conductive material of the polymeric material used to form the conductive composite particles as discussed above can be applied to the conductive polymer fibers, nonwoven materials and structures (e.g., , Webs, veils, fleece, fabrics, fiber preforms, etc.).

Conductive polymeric fibers can be produced by techniques known in the art for the manufacture of synthetic fibers. Preferably, the conductive polymer fibers are obtained by continuous extrusion of the polymer / conductive blend into a reel, followed by mechanical stretching by heating. More preferably, the molten form of the polymer / conductive blend is drawn in an elemental form, cooled, and then heated and mechanically stretched to orient the polymer chains and make the composite conductive element elastomeric and soluble, . Stretching may include pulling the extruded element in air for a desired distance, e.g., 50 to 500 mm. In one embodiment, the polymer / conductive blend in pellets or other extrudable form is fed to an extruder having a die head (or the like) with openings or slots in the desired number.

The fibers can be prepared as multi-filaments ranging from a molten polymer / conductive blend, stretched to 20 filaments that are cooled, optionally twisted as desired, and then heated and stretched.

Conductive polymer fibers can be selected from the group consisting of spun fibers, extruded fibers, cast strands, continuous strands, continuous fibers, bi or multi component fibers, random fibers, staple fibers, Filaments, yarns, whiskers, hollow fibers and filaments, and mixtures thereof. The fibers may be a plurality of mono-filaments or yarns of single and multiple mono-filaments. Moreover, the fibers may have cross-sections with more complex structures such as sheath / core, side / side, pie segment configuration or sea-island configuration, which may be composed of different polymers or blends thereof. Conductive polymeric fibers may contain additional organic or inorganic fillers or modifiers. Preferably, the fibers or yarns comprise fiber filaments each having a diameter of about 100 [mu] m.

The conductive nonwoven materials formed from the conductive polymeric fibers can take the form of nonwoven mat, web, fleece, and bale, which can be formed using conventional fabrication techniques such as wet-laying, carding, air-laying, spunbonding, , Flash rotation, electrostatic rotation, water-jet punching and needle punching techniques.

In spunbonding, the pellets of the conductor / polymer blend are fed to an extruder and forced through a plurality of spinnerets to form a continuous filament of molten product. The filaments are cooled by air flow means in the air flow area, stretched by aerodynamic force and then transported to the downstream exit channel. The filaments are deposited as a nonwoven web of random fibers onto a wire mesh conveyor. The web is transferred to the bonding calender when heat and pressure are applied to set the final product. After cooling, the web may be wound.

In the melt blowing process, the conductor / polymer blend in the melt form is extruded through a die containing hundreds of small holes. The flow of hot air from the left and right sides of the die rapidly attenuates the extruded polymer stream to form the microfine filaments. The filaments are then blown onto the collector screen by high velocity air, thereby forming a self-bonded nonwoven web. Alternatively, extruded continuous filaments can be compacted into pieces, then scattered onto a heated mandrel to form a nonwoven web, and then cooled.

The nonwoven bale for use in composite materials can be produced by the discussed nonwoven fabrication process without the need for any textile weaving technique. Such a veil may take the form of a mat or web composed of randomly arranged continuous or spun fibers. The composition of the fibers includes both the polymeric component and the conductive component, as in the case of the conductive composite particles discussed above. As such, the conductive polymeric fibers have properties similar to those of the conductive composite particles. The nonwoven bale is associated with adjacent files of dried structured reinforcing fibers (e.g., carbon fibers) in a dry fiber preform employed for liquid resin injection as interlining between two adjacent prepreg files during prepreg layup So that they are particularly suitable for interposition therebetween at the time of contact.

In the resin injection, a dry fiber preform (no resin) is injected together with the curable, liquid resin composition. When a nonwoven bale comprised of conductive polymeric fibers is incorporated into such a dry fiber preform, the polymeric component of the conductive polymeric fibers in the veil maintains its solid phase during resin injection. Then, during the curing of the resin-impregnated fiber preform, the polymeric component undergoes phase transitions into the fluid phase by dissolving in the resin.

When a nonwoven bale comprised of conductive polymeric fibers is used for prepregging, the polymeric component of the conductive polymeric fibers in the veil maintains its solid phase during prepreg layup, and then during curing, And undergoes phase transformation into the fluid phase by dissolving it in the resin matrix of the prepreg files as discussed above.

In another embodiment, the conductive polymeric fibers are part of a adapted structural fiber preform adapted for resin injection, wherein the structural preform is comprised of reinforcing fibers in combination with conductive polymeric fibers. Moreover, the structural preform can be shaped into a three-dimensional configuration according to the shape of the final composite structure to be manufactured. The fibers are assembled in such a way as to provide their physical association. Combinations for providing a physical association may be made by any of the methods known in the textile arts such as stitching, knitting, crimping, punching, weaving, braiding, over-winding, meshing, blending, alignment, twisting, coiling, , Placement in the same layer of fibers disposed in different but adjacent layers of fibers, and the like. Conductive polymeric fibers can be arranged as misaligned or misaligned, or stitched, between the reinforcing fibers, or as multifilament yarns composed of a plurality of conductive composite fibers and reinforcing fibers. In this context, the reinforcing fibers are fibers consisting of carbon, glass, inorganic oxide, aramid, carbide, boron, ceramic, metal, metal coated fibers or combinations thereof. The structural fiber preform is then injected with the curable, liquid resin composition and then cured to form a composite structure having conductive properties. The polymeric component of the conductive polymer fibers undergoes the same liquid phase transition during curing as discussed above with reference to conductive composite particles.

Also contemplated herein are non-crimped fibers comprised of a combination of reinforcing fibers and conductive polymer fibers. By " non-crimped " is meant a fabric that is deformed into a fabric by stitching or by the application of a binder so that the layers of fibers lie on top of each other and the fibers remain straight without substantial crimps. Conductive polymeric fibers can be present in one or more layers of non-crimped fabrics. Moreover, the conductive polymer fibers may be non-uniformly present with respect to the reinforcing fibers to locally impart properties such as z-direction conductivity and toughening. Such a non-crimped fabric may be incorporated into a structured fiber preform that has been modified for resin injection.

Usage

The composite materials of the present invention find use in any field where they are required to impart improved conductivity to the composite material / structure. According to one embodiment of the present invention, the z-direction conductivity of the composites of the present invention is at least one order of magnitude greater than the measured values for conventional 3-generation carbon fiber reinforced materials.

The composite materials of the present invention can be applied to the manufacture of components (e.g., aerospace, aviation, offshore and onshore vehicles) for transport applications and can be used for the production of primary and secondary aircraft structures (fuselage, ), Space and ballistic structures. The composite materials of the present invention find use in the construction / construction field. Moreover, the composite materials of the present invention, particularly prepregs and prepreg layups, are particularly suitable for the production of load-bearing or impact-resistant structures.

Example

The following examples serve to illustrate some preferred embodiments of the present invention and their test results, but they should not be construed as limiting the scope of the invention in any way.

Measuring methods

In the following examples, the following measurement methods were used:

Z-direction DC  Electrical conductivity

The electrical conductivity of the cured composites was measured by an average of Burster-Resistomat 2316 milliohmmeter write resistance values as a ratio between applied voltage and current in the bridge method. Kelvin test probes were used to create a contact between two sample surfaces. All measurements were performed according to the 4-wire measurement method at room temperature (RT), under standard humidity conditions.

Measurements were performed on coupons extracted from defect-free panels prepared in accordance with EN 2565 Method B. Approximately 2 mm thick quasi-isotropic square samples (side length = 40 mm +/- 0.1 mm) were characterized.

Composite test specimen surfaces were prepared by providing an upper resin-rich layer to expose the underlying carbon fibers to ensure direct contact with the electrodes. A commercial silver paste was then used to create two electrodes on the opposite coupon surfaces. At least five samples per lay-up and lay-up were tested.

The DC electrical conductivity was calculated as [S / m] according to the following equation:

Where: R is the measured resistance [ohm];

l is the sample thickness [m];

S is the sample surface area [m ² ]

Particle size distribution

The particle size distribution was measured using a Malvern Mastersizer 2000 operating in the range of 0.02 μm to 2000 μm.

Example  One

Preparation of nickel-based conductive composite particles

An amount of filamentous nickel (Ni) flake (525 nickel powder available from Novamet) in an amount sufficient to achieve a final concentration of 70 wt.% Was passed through a melt mixing process in a twin screw extruder (Sumikaexel 5003P) 0.0 > (PES) < / RTI > polymer. Pure samples of the same PES polymer were used as controls. High-shear screw profiles were used to optimize the dispersion level. The profiles include conventional mixing segments associated with mixing units of chaos to produce an optimal balance between shear and pressure forces in the barrel of the extruder. The temperature profile and process conditions used are reported in Table 1.

The resultant Ni / PES blend was applied to cryogenic grinding to produce micro-sized particles having an average particle size of less than 60 [mu] m using an Alpine cryogenic milling system equipped with different rotating milling media - particles "). Specifically, multiple passes using stud beaters, swing beaters and plate beaters were required to achieve a target particle size distribution. Figure 4 shows a SEM image of micron-sized, composite Ni / PES particles produced as a result of cryogenic grinding.

Example  2

Effect of nickel-based conductive micro-particles on electrical performance of composite structures

Example 1 of the composite nickel / PES micro-particles Cytec Engineered Materials Ltd, a CYCOM ^® 977-2-34% -194-IMS24K unidirectional tape supplied by the UK (epoxy-based matrix of the unidirectional carbon fibers impregnated with) a Dispersed through the surface spraying process. The particle load was 10% by volume based on the total resin volume in the tape. A plurality of such tapes were laid up on top of each other with microparticles located between adjacent tapes to form a 1.5 mm thick quasi-isotropic test panel. The panel was then cured in an autoclave at a curing period of 2 hours at < RTI ID = 0.0 > 180 C. < / RTI > These test panels were labeled "2A".

During the curing process, the particles were located within a resin-rich zone between adjacent carbon fiber layers defining an interlayer region. The thermoplastic component of the composite micro-particles was dissolved in the epoxy-based matrix of the tapes during the curing period and the metal component was released (as conductive particles) into interlayer areas of the multi-layered panel. In that way, localized conductive scaffolds or bridges were created between adjacent carbon fiber layers.

For comparative purposes, a similar test panel labeled " Reference 1 " was prepared by the same method, but the composite PES / nickel microparticles were replaced by non-conductive, crosslinked thermoplastic (TP) particles. The z-direction conductivity for the two test panels is shown in Table 2.

The controlled introduction of composite Ni / PES micro-particles within the interlaminar areas of panel 2A was determined to produce one or more orders of improved size in z-directional conductivity, as compared to reference one panel. The reduction in composite volume resistance is believed to be the result of an increased number of electrical bridges created through the controlled dissolution mechanism of the composite Ni / PES micro-particles.

Example  3

Effect of Conductive Interlayer Particle Loading on Mechanical Performance of Composite Structures

Surface of the two different load of particles (10% and 20% by volume) is CYCOM 977-2-34% ^® from Cytec Engineered Materials UK -194-IMS24K unidirectional tape - Example 2 The same composite Ni / PES used for the micro- . ≪ / RTI > Two test panels with two different particle loads were formed by laying up the tapes with micro-particles dispersed thereon. The resulting test panels were evaluated to determine the effect of composite micro-particles on thermo-mechanical properties. A test panel containing 10% micro-particles was labeled as " 3B ", and a test panel containing 20% micro-particles was labeled as " 3C ". For comparative purposes, similar test panels containing no composite Ni / PES micro-particles were prepared and labeled as "reference 2 ".

The mechanical performance of the test panels is shown in Table 3.

The introduction of 10 vol.% And 20 vol.% Of the composite Ni / PES particles in panels 3B and 3C were respectively determined to produce 60% and 73% improvement in delamination growth resistance in model I as compared to reference 2 panel. A simultaneous 10% to 15% increase in peel growth resistance was also observed in Mode II values. In addition, the introduction of 10% of the composite Ni / PES micro-particles resulted in a 25% increase in compressive strength after 30 J impact, while significantly reducing the damaged area.

Example  4

Influence of silver-based conductive micro-particles on the mechanical performance of composite structures

A sufficient amount of silver (Ag) powder CAP9 (from Johnson Matthey, UK) was dispersed in a commercially available functionalized polyethersulfone polymer (Sumitomo to SUMIKAEXEL 5003P) through a melt-mixing process in a twin screw extruder to form a composite blend + ≪ / RTI > conductive component) of 70% by weight. High-shear screw profiles were used. The temperature profile and process conditions used are shown in Table 1.

The pellets produced from the extruder were sequentially pulverized in a cryogenic grinding apparatus to produce composite Ag / PES micro-particles having an average particle size of less than 60 μm.

Composite materials with micro-particles of the bar CYCOM ^® 977-2-34% -194-IMS5131-24K unidirectional tape were sprayed onto the surface, a plurality of tape results were ray-up is given as described in Example 2 to form an isotropic panel . The panel was then cured at 180 占 폚 for 3 hours in an autoclave. Based on the total resin content in the panel, 10% by volume of particle loading was selected for this example. The panel of results was labeled as " 4A ".

The z-direction conductivity of the 4A panel was measured according to the above method. Table 4 shows a comparison of the z-direction conductivity between the 4A panel and the Reference 1 panel described in Example 2. [

The incorporation of the composite Ag / PES micro-particles was found to produce more than half of the improved size of the z-directional conductivity, compared to the reference 1 panel.

Example  5

Effect of Polymeric Components of Conductive Composite Microparticles on the Mechanical Performance of Composite Structures

An alternative conductive composite blend " 5A " is a commercially available granulated copper (Cu) (CH-L7 from GGP Metalpowder AG) as described in Example 1 in a commercially available functionalized polyethersulfone (PES) polymer SUMIKAEXEL 5003P from Sumitomo, UK). A copper concentration of 65 wt% was obtained based on the total weight of the composite blend.

For comparison purposes, the conductive composite blend " 5B " was prepared by mixing the same amount (65% by weight) of copper material in a commercially available polyamide (VESTOSINT 2159 available from Evonik, UK) using the twin screw extruder described in Example 1 . The process conditions are shown in Table 5.

In both cases, the pellets produced from the extruder were milled in a cryogenic mill to produce conductive composite micro-particles having an average size (d50) of less than 50 [mu] m. The micro-particles were then dispersed onto the surface of the 977-2-34% -194-IMS24K unidirectional tape at 10 vol% particle loading based on the total resin content in the tape prior to layup. A plurality of such tapes were laid up in an interleaved stacking sequence to form the panels as described in Example 2. The panel was then cured at 180 DEG C for 3 hours in an autoclave.

The Z-direction conductivity values were recorded as previously described and the results are shown in Table 6. The " Reference 1 " panel as described in Example 2 is used herein for comparison.

Figure 5a shows a cross-sectional view of a cured panel (5B) containing Cu / polyamide composite particles in an interlayer region, and Figure 5b is an exploded view (in a darkened area) of a part of the interlayer region. It can be seen from FIGS. 5A and 5B that the polyamide-based particles are not efficiently dissolved into the epoxy matrix during the curing period, thereby limiting the formation of electrical bridges between the layers of carbon fibers. Thus, the introduction of composite particles within the interlaminar region of the laminated panel did not result in any significant improvement in z-directional conductivity compared to the standard non-conductive thermoplastic interleaved panel (Ref. 1).

In contrast, the PES-based particles in the panel 5A were substantially dissolved into the epoxy matrix during the curing period and released the copper particles into interlayer areas of the composite panel. In such a manner, a conductive scaffold or bridge is created between adjacent carbon fiber layers. Figure 6 shows a cross-sectional view of a cured panel 5A containing 10% by volume of Cu / PES composite particles. As a result of the controlled dissolution mechanism, Cu / PES composite particles have been found to provide almost one dimensional improvement in z-direction conductivity compared to non-conductive thermoplastic particles.

The results further indicate that the selection of suitable polymeric components for the conductive composite particles is important in achieving the dissolution mechanism, which in turn provides an improvement in the z-direction conductivity for the composite structures.

Example  6

Effect of conductive particles: ratio of non-conductive particles to electrical performance of the composite

Four different panels 7A-7D were fabricated using the conductive composite Cu / PES particles described in Example 5 and non-conductive thermoplastic (TP) particles as described in Example 2 to provide different conductive particles : Manufactured and cured at a ratio of non-conductive particles. The z-direction conductivity of the cured panels was measured and the results are shown in Table 7. The " Reference 1 " panel as described in Example 2 is used herein for comparison.

As shown in Table 7, there is a clear improvement trend in z-direction conductivity with increasing loading of Cu / PES composite particles.

The ranges described herein are inclusive and independently combinable (e.g., a range of about 25 vol% or less, or more specifically, about 5 vol% to about 20 vol% All intermediate values in the range).

While various implementations are described herein, it will be appreciated that various combinations of elements, variations, or improvements herein may be made by those skilled in the art from the written description and are within the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material in accordance with the teachings of the invention without departing from the essential scope thereof. Accordingly, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (37)

i) at least one structural layer of reinforcing fibers impregnated with a curable resin matrix; And
ii) at least one electrically conductive composite particle adjacent or in close proximity to the reinforcing fibers, wherein the conductive composite particle comprises a conductive component and a polymeric component, wherein the polymeric component of the conductive composite particle is initially a solid phase And which is substantially insoluble in the curable resin matrix prior to curing of the composite material but which is capable of undergoing at least partial phase transition into the fluid phase by dissolving in the resin matrix during the curing period of the composite material, Containing curable composites. The curable resin matrix of claim 1, wherein the curable resin matrix is soluble in the resin matrix during curing of the composite material wherein at least 50% of the polymeric component of the conductive composite particles is phase transitioned to the fluid phase, Wherein the polymeric component is a thermosetting composition. The composite material according to claim 1 or 2, wherein the conductive component of the electrically conductive composite particle comprises one or more electrically conductive materials each having an electrical conductivity of more than 1 x 10 ³ S / m. 4. The method of any one of claims 1 to 3, wherein the conductive component of each electrically conductive composite particle is a composite comprising at least one conductive material selected from metallic materials, non-metallic conductive materials, and combinations thereof material. The method of any one of claims 1 to 3, wherein the conductive component of the electrically conductive composite particle is selected from silver, gold, platinum, palladium, nickel, copper, lead, tin, aluminum, titanium, A composite material comprising one or more metallic materials. The composite material according to any one of claims 1 to 3, wherein the electrically conductive composite particle comprises one or more non-metallic conductive materials selected from carbon, graphene, graphite, and combinations thereof. The composite material according to any one of claims 1 to 6, wherein the polymeric component comprises polyethersulfone. The conductive composite particle of any one of claims 1 to 7, wherein the polymeric component of the conductive composite particle is selected from the group consisting of polyurethane, polyketone, polyamide, polyphthalamide, polystyrene, polybutadiene, polyacrylate, polyacryl, polymethacrylate , Polyethersulphone (PES), polyetherether sulfone (PEES), polyphenylsulfone, polysulfone, polyester, liquid crystal polymers, polyimide, polyetherimide (PEI), polyether ketone ketone polyetheretherketone (PEEK), polyurethane, polyaryl ether, polyaryl sulfide, polyphenylene oxide, polyphenylene oxide (PPO), polyethylene oxide (PEO), polyetheretherketone , Polypropylene oxide, copolymers and combinations thereof, at least one selected from the group consisting of A composite material comprising one thermoplastic polymer. The composite material according to any one of claims 1 to 8, wherein the polymeric component of the conductive composite particle further comprises at least one thermosetting resin. The composite material according to claim 9, wherein the polymeric component of the conductive composite particle further comprises a curing agent or a catalyst. The composite material according to any one of claims 1 to 10, wherein the conductive component of the conductive composite particle, relative to the total weight of the conductive composite particles, has a weight content of 1% to 90%. The composite material according to any one of claims 1 to 11, wherein the plurality of electrically conductive composite particles are present in an amount of from 0.1% by volume to 25% by volume based on the volume of the total resin content in the composite material. The composite material of any one of claims 1 to 12, wherein a plurality of electrically conductive composite particles are present, and wherein the particles have an average particle size of less than 150 μm. 14. A composite material according to any one of claims 1 to 13, wherein a plurality of electrically conductive composite particles are present, and wherein said particles have an average particle size in the range of 10 [mu] m to 60 [mu] m. The conductive composite particles of any one of claims 1 to 14, further comprising non-conductive particles, wherein the conductive composite particles in combination with the non-conductive particles are selected from the group consisting of 25 A composite material present in a content of less than or equal to volume percent. The curable resin matrix according to any one of claims 1 to 15, wherein the curable resin matrix is selected from the group consisting of epoxy resins, bismaleimide, vinyl ester resins, cyanate ester resins, isocyanate-modified epoxy resins, phenolic resins, , Formaldehyde condensate resins, polyesters, acrylics, and combinations thereof. ≪ RTI ID = 0.0 > 11. < / RTI > 16. The method of any one of claims 1 to 16, further comprising a second structural layer of reinforcing fibers impregnated with a curable resin matrix, wherein the at least one conductive composite particle comprises a first structural layer and a second structural layer, A composite material positioned between reinforcing fiber layers. A structural layer of reinforcing fibers impregnated with a first curable resin matrix; And
A layer of a second curable resin matrix in contact with one of the two opposing surfaces of the structural layer,
Wherein the second curable resin matrix comprises a plurality of conductive composite particles, wherein the first curable resin matrix is free of any composite conductive particles,
Wherein the conductive composite particles each comprise a conductive component and a polymeric component and wherein the polymeric component is initially in a solid phase and is substantially insoluble in the curable resin matrix prior to curing of the composite laminate, And at least one polymer capable of undergoing at least partial phase transition into the fluid phase by dissolving in the second resin matrix during the curing period. 19. The method of claim 18,
Further comprising an additional layer of the second curable resin matrix in contact with the other of the two opposing surfaces of the structural layer. (a) dispersing at least one conductive material in a polymeric material to form a composite blend;
(b) optionally heat treating the blend;
(c) forming micron-sized conductive composite particles having an average particle size of less than 150 [mu] m from the composite blend;
(d) optionally heat treating the micron-sized conductive composite particles; And
(e) forming a composite material comprising at least one layer of reinforcing fibers impregnated with a curable resin matrix, and a plurality of micron-sized conductive composite particles adjacent to said reinforcing fibers,
Wherein each of the polymeric materials in the conductive composite particle is initially in a solid phase and is substantially insoluble in the curable resin matrix prior to curing of the resin matrix but is dissolved in the matrix of the resin during the curing period of the composite material to form a fluid phase ≪ / RTI > wherein the at least one polymer comprises at least one polymer capable of undergoing at least partial phase transition of the polymer. The method of claim 20,
(f) curing the composite material, wherein the polymeric material in the conductive composite particles dissolves in the resin matrix during curing to undergo at least partial phase transition to the fluid phase,
Wherein after the curing, the conductive component of the conductive composite particles functions as a conductive bridge between adjacent layers of the reinforcing fibers. The method of claim 20 or 21, wherein the curable resin matrix is a thermoset composition that is soluble during curing of at least 50% of the polymeric components of each conductive composite particle. 21. The method of claim 20, wherein step (a) is performed in an extruder, and wherein the extruded composite blend is in the form of pellets. 24. The method of claim 23, wherein step (c) is performed by cryogenic grinding. The method of any one of claims 20 to 24, wherein the conductive material to be dispersed in step (a) is selected from the group consisting of flakes, powders, dendrites, fibers, spheres, metal- ≪ / RTI > and combinations thereof. The conductive component of any one of claims 20 to 24, wherein the conductive component of the electrically conductive composite particle is one selected from silver, gold, platinum, palladium, nickel, copper, lead, tin, aluminum, titanium, RTI ID = 0.0 > 1, < / RTI > 25. The method of any one of claims 20 to 24, wherein the electrically conductive material is selected from the group consisting of chopped carbon fibers, graphite flakes, graphite nano-platelets, carbon black, single- Walled carbon nanotubes (DWCNT), multi-walled carbon nanotubes (SWCNTs), single-walled carbon nanotubes carbon nano-tubes, MWCNT), carbon nano-fibers, carbon nano-spheres, carbon nanorods, fullerenes, carbon nano-ropes, carbon nano- Wherein the method is selected from the group consisting of needles, carbon nano-sheets, graphens, carbon nano-cones, carbon nano-scrolls with scroll-shaped features, boron nitride-based products. 28. The method of any one of claims 20 to 27, wherein the composite material is formed by impregnating the layer of reinforcing fibers with the curable resin matrix, the conductive composite particles being incorporated into the curable resin matrix prior to resin impregnation, Wherein the conductive composite particles are left on the outer surface of the layer of reinforcing fibers after impregnation. 21. The method of claim 20, wherein the composite material comprises a layer of a curable resin matrix free of conductive composite particles, contacting the layer of the layers of reinforcing fibers, and then causing the resin matrix to impregnate the reinforcing fibers by application of heat and pressure step; And
Sequentially forming a second layer of the resin matrix containing the conductive composite particles in contact with the surface of the impregnated reinforcing fiber layer. 21. The method of claim 20,
Contacting two layers of a curable resin matrix free of conductive composite particles with an opposing surface of the reinforcing fiber layer and then causing the resin matrix to impregnate the reinforcing fibers by application of heat and pressure; And
And then the layer of the resin matrix containing the conductive composite particles is brought into contact with the surface of the resin-impregnated reinforcing fibers. At least one structural layer of reinforcing fibers impregnated with a curable resin matrix; And
A nonwoven bale adjacent said structural layer, said bale comprising randomly aligned conductive polymeric fibers, said conductive polymeric fibers each comprising a conductive component and a polymeric component,
Wherein the polymeric components of the conductive polymeric fibers are each initially in a solid phase and are substantially insoluble in the curable resin matrix prior to curing the curable resin matrix, And at least one polymer capable of undergoing at least partial phase transformation. One or more layers of resin-free reinforcing fibers; And
At least one nonwoven bale comprising randomly arranged conductive polymeric fibers, wherein the conductive polymeric fibers each comprise a conductive component and a polymeric component,
Here, the polymeric components of the conductive polymeric fibers are each initially in a solid phase and are substantially insoluble in the curable resin composition to be introduced into the preform by resin injection, but the fluidic phase during the curing period of the resin- And at least one polymer that is capable of undergoing at least partial phase transition into the polymeric matrix. (a) laying up two or more structural layers of reinforcing fibers impregnated with a curable resin matrix to form a layup;
(b) randomly disposed conductive polymeric fibers, each of the conductive polymeric fibers having at least one nonwoven bale comprising a conductive component and a polymeric component disposed between two adjacent structural layers, ; And
(c) curing the layup,
Wherein the polymeric components of the conductive polymeric fibers are each initially in a solid phase and are substantially insoluble in the curable resin matrix prior to curing of the layup and then during curing the polymeric material is present in the resin matrix And at least one polymer that undergoes at least partial phase transition into the fluid phase upon dissolution. (a) a conductive polymeric fiber disposed between (i) multiple layers of dry fibers and (ii) two adjacent fiber layers, wherein each of the conductive polymeric fibers comprises a conductive component and a polymeric component Forming a preform comprising at least one nonwoven bail;
(b) injecting a dry fiber preform into the curable liquid resin composition; And
(c) curing the resin-injected fiber preform,
Wherein the polymeric components of the conductive polymeric fibers are each initially in a solid phase and are substantially insoluble in the curable resin composition prior to injection of the resin-injected fiber preform and prior to curing thereof, Wherein the gelling component comprises at least one polymer dissolved in the resin composition to undergo at least partial phase transition into the fluid phase. 1. A structural fiber preform adapted for resin injection, the structural fiber preform comprising reinforcing fibers physically associated with conductive polymeric fibers,
Wherein each of the conductive polymeric fibers comprises a conductive component and a polymeric component wherein the polymeric component of the conductive polymeric fiber is in each case initially in a solid phase and is present in the curable resin composition to be injected into the preform during resin injection Wherein the at least one polymer is substantially insoluble but can undergo at least partial phase transition to the fluid phase during the curing period of the resin-injected preform. 41. The structural preform according to claim 35, wherein the physical linkage of the fibers is selected from co-mingling, aligning in the same layer of fibers, and positioning in different but adjacent layers of fibers. 1. A structural preform adapted for resin injection, said structural preform comprising a plurality of fabric ply, at least one of which is comprised of reinforcing fibers and conductive polymeric fibers,
Wherein each of the conductive polymeric fibers comprises a conductive component and a polymeric component wherein each of the polymeric components of the conductive polymeric fibers is present in a solid phase initially and comprises at least one polymeric component in the curable resin composition to be introduced into the preform during resin injection A structured preform adapted for resin injection that is substantially insoluble, but which comprises at least one polymer capable of undergoing at least partial phase transition into the fluid phase during the curing period of the resin-injected preform.

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